Polyolefin-based composition for a lid and methods of making and using

ABSTRACT

Aspects of the present disclosure relate to a polyolefin composition and processes suitable for use in forming a lid for a hot food or beverage container that has a stiffness comparable to a similar lid made using high impact polystyrene and a density less than water at 23° C.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 16/150,036, filed Oct. 2, 2018, now allowed, which applicationclaims the benefit of U.S. Provisional Patent Application No.62/570,222, filed Oct. 10, 2017, both of which are incorporated hereinby reference in their entirety.

BACKGROUND

Polystyrene is commonly used for forming disposable containers, cups,lids, and other food service articles. Polystyrene has a stiffness andheat resistance suitable for use in making food service articles for usein hot food service, such as coffee cup and soup bowl lids. However,polystyrene can be challenging to recycle, dissuading some consumersfrom purchasing products made using polystyrene. In the United States,an increasing number of municipalities are banning or placingrestrictions on the use of polystyrene in food service articles due topoor public perception.

BRIEF SUMMARY

According to one aspect, a lid for a food or beverage container is madefrom a sheet comprising at least one polyolefin with at least onefiller. The sheet includes a plurality of expanded cells providing thelid with a density of less than 1 g/cm³ at 23° C.

In another aspect, a process for forming a lid for a food or beveragecontainer is provided. The process includes providing a polyolefin blendincluding at least one polyolefin and at least one filler to anextruder. A blowing agent is provided to the polyolefin blend. Thepolyolefin blend is extruded to form a polyolefin-based sheet and thepolyolefin-based sheet is at least partially expanded to form aplurality of expanded cells within the sheet. The expandedpolyolefin-based sheet can be formed into the shape of a lid. The lidcan have a density less than water at 23° C.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a perspective view of an exemplary hot cup lid according to anaspect of the disclosure.

FIG. 2 is a cross-sectional view of an exemplary hot cup lid having aplurality of expanded cells according to an aspect of the disclosure.

FIG. 3 is a cross-sectional view of an exemplary hot cup lid having aplurality of expanded cells according to an aspect of the disclosure.

FIG. 4 is a cross-sectional view of a polypropylene-based hot cup lidthat does not exhibit a plurality of expanded cells.

FIG. 5 is a photograph illustrating the ability of a hot cup lid havinga plurality of expanded cells to float in water according to an aspectof the disclosure.

FIG. 6 is top-down view of a hot cup lid indicating the hot deflectiontest measurement points according to an aspect of the disclosure.

DETAILED DESCRIPTION

Aspects of the present disclosure relate to a polyolefin composition andprocesses suitable for use in forming a lid for a food servicecontainer, such as a hot food or beverage container, having a stiffnesscomparable to a conventional lid made using high impact polystyrene(HIPS) such that the polyolefin-based lid can be used as a replacementof the polystyrene-based lid. In addition, the polyolefin compositionand processes of the present disclosure provide a lid that is alsorecyclable using conventional practices that rely on capturingrecyclable material floating in a recycling stream. According to anotheraspect of the present disclosure, recyclability of the polyolefin-basedlid can be maintained by configuring the polyolefin composition suchthat the lid has a density less than 1 g/cm³ at 23° C. such that thepolyolefin-based lid floats in the recycling stream.

Aspects of the present disclosure relate to a polyolefin composition forforming a polyolefin-based sheet having a stiffness suitable for use informing a lid for a hot beverage or food container in combination with adensity suitable for recycling. The polyolefin composition can be usedto form a polyolefin-based sheet that can be thermoformed or molded intothe desired lid shape. While aspects of the present disclosure arediscussed in the context of a lid for use with a cup intended to hold ahot liquid, aspects of the present disclosure can be used in a similarmanner to form a polyolefin-based sheet that can be thermoformed ormolded into the shape of other articles, such as soup containers andlids, for example. In addition, aspects of the present disclosure arenot limited to use with hot food and beverages, but may be used withroom temperature or chilled food and beverages.

FIG. 1 illustrates an exemplary cup lid 10 that may be formed bythermoforming a polyolefin-based sheet according to an aspect of thepresent disclosure. The cup lid 10 can have any desired shape andoptionally the same shape as a conventional dome-shaped cup lid that isused with a cup intended to hold a hot beverage, such as coffee or tea.The polyolefin-based sheet can be used to form lids having other shapes,including other dome-shaped, flat, or frusto-conical shaped lids in amanner similar to what is described in the present disclosure.

Conventional coffee cup lids are often made using unexpanded high impactpolystyrene (HIPS). Cup lids made by thermoforming HIPS sheets have ahigh heat deflection temperature (HDT), also referred to as high heatresistance. A material having a high HDT, such as HIPS, increases theresistance of the lid to heat distortion that can occur when the lid isplaced on a container holding a hot liquid or when the lid is reheated,such as when the container and lid are placed in a microwave for heatingthe contents of the container. Polyolefins, such as polypropylene,generally have a flexural modulus less than that of HIPS, particularlyat hot food service temperatures, and thus typically present a challengefor use in forming a hot cup lid. A cup lid made using a polypropylenehaving a low flexural modulus may become soft and/or weaken when the cuplid is placed on a cup holding a hot liquid or when the cup lid isreheated.

According to an aspect of the present disclosure, a polyolefincomposition includes at least one polyolefin and at least one filler foruse in forming a polyolefin-based sheet that can be shaped into a lidhaving a stiffness that is at least comparable to a similar lid madefrom unexpanded HIPS at temperatures typically experienced by lids usedin hot food service. Hot food service temperatures are typicallyconsidered to be about 90° C. or greater. As used herein, comparable isused to refer to a characteristic that is within +/−15%, optionallywithin +/−10%, and further optionally within +/−5% of the referencematerial or article. As used herein, a lid is similar to another lidwhen the lid dimensions and/or part weight are comparable such that thesimilar lids can be used interchangeably on a container.

The at least one polyolefin and the at least one filler, and optionallyother additives, can be combined to form a blend suitable for extrusionthrough a die to form the polyolefin-based sheet. Extrusion refers to aprocess for shaping or forming an article by moving material through adie opening by forcing, pressing, and/or pushing the material throughthe die opening. The die opening can be an orifice having any desiredshape, such as a slit. The polyolefin-based blend can be extrudedthrough the die into a sheet or a cylinder that is subsequently cut toform a sheet for shaping into a lid. Extrusion can be performedcontinuously to form a long sheet or cylinder or can be semi-continuoussuch that multiple shorter segments are produced for later shaping intoa lid. The lid production process may include in-line extrusionthermoforming or off-line extrusion thermoforming. Extrusion can beperformed using a single screw extruder or a twin screw extruder,although the present disclosure is not limited to any particularextrusion device or die.

In one aspect of the present disclosure, thermoforming is performed onthe materials exiting the extruder while they are still in molten/heatedform from the extrusion process. The molten sheets from the extruder canbe thermoformed. In another aspect, the extruded sheets can be allowedto cool to room temperature and solidify following extrusion. Thesolidified sheets can then be reheated for forming using a reciprocatingformer.

The amount and type of filler combined with the polyolefin to form theextrusion blend is selected to provide a polyolefin-based sheet that canbe used to form a lid having a stiffness that is at least comparable toand optionally greater than that of a similar lid made from unexpandedHIPS. Optionally, the amount and type of filler are selected to providethe polyolefin-based sheet with a shrinkage rate less than apolypropylene sheet without filler. In one example, the amount and typeof filler are selected to provide the polyolefin-based sheet with ashrinkage rate of about 0.013 inches (0.33 mm) to 0.015 inches (0.38 mm)per inch (25.4 mm), or about 1.3 to 1.5%, during storage after formingthe lid. The shrinkage rate during sheet formation and trimming can beabout 1.4% or 0.014 inches (0.36 mm) per inch (25.4 mm).

Non-limiting examples of suitable polyolefins include polypropylenehomopolymers, polypropylene impact copolymers, ethylene-propylenecopolymers, high density polyethylene, and combinations thereof.Copolymers of polypropylene can include copolymers in which the polymeris derived from polypropylene monomers and at least one other species ofmonomer or a block copolymer derived from blocks of polypropylenemonomers and blocks derived from at least one other species of monomer,non-limiting examples of which include ethylene, propylene, or acombination of ethylene and propylene.

According to one aspect of the present disclosure, the polyolefinincludes a polypropylene that is a high modulus polypropylenehomopolymer having a flexural modulus of at least about 290,000 psi,optionally at least about 300,000 psi, as measured according to ASTMD-790A. Optionally, the polyolefin is a high crystalline polypropylenecharacterized by low xylene solubles (XS), which is generally consideredto be related to isotacticity and crystallinity. When compared tostandard homopolymer resins, high crystalline polypropylene exhibits ahigher stiffness and increased chemical and heat resistance. In oneaspect, the polyolefin is a high crystalline polypropylene having aflexural modulus of at least about 290,000 psi, optionally at leastabout 300,000 psi, and further optionally about 290,000 to 300,000 psi,as measured according to ASTM D-790A. In another aspect, polypropyleneshaving an HDT of at least about 95° C., optionally at least about 105°C., further optionally at least about 115° C. at 66 psi, as measuredaccording to ASTM D648, may be used.

According to another aspect, preferred polypropylenes have a modulus ofelasticity, as measured by Dynamic Mechanical Analysis (DMA), of atleast about 160,000 psi, optionally at least about 210,000 psi, furtheroptionally at least about 230,000 psi at temperatures corresponding tohot drink temperatures according to ASTM D4065 and ASTM E2254-03. Anexample of a hot drink temperature includes 90° C.

In one aspect of the present disclosure, the polyolefin includes atleast one polypropylene having a flexural modulus of at least about290,000 psi, optionally at least about 300,000 psi, an HDT of at leastabout 95° C., optionally at least about 105° C., further optionally atleast about 115° C., and/or a modulus of elasticity of at least about160,000 psi, optionally at least about 210,000 psi, further optionallyat least about 230,000 psi.

The filler can be a mineral filler, a natural fiber-based filler, orcombinations thereof. Non-limiting examples of suitable mineral fillersinclude talc, calcium carbonate, mica, wollastonite, and combinationsthereof. Non-limiting examples of suitable natural fiber-based fillersinclude wood fiber, paper powder, cellulose fiber, and combinationsthereof. Optional additives for use with the polyolefin compositioninclude colorants and processing aids.

The thickness of the extruded sheet, when used for forming lids, can beabout 0.035 inches (0.9 mm) or less, optionally about 0.025 inches (0.6mm) or less. The thickness of the lid formed from the extruded sheet canvary depending on the lid design, but can be less than about 0.01 inches(0.25 mm), optionally less than about 0.015 inches (0.4 mm), furtheroptionally less than about 0.025 inches (0.6 mm), still furtheroptionally less than about 0.035 inches (0.9 mm), and further optionallywithin the range of about 0.015 to 0.018 inches (0.4 to 0.46 mm).

The polyolefin composition is also treated such that the sheet formedusing the polyolefin composition has a plurality of expanded cellsformed within the sheet to provide the sheet with an expanded cellularstructure to decrease the density of the extruded polyolefin-based sheetcompared to a similar polyolefin-based sheet that has not been treated.According to an aspect of the present disclosure, the cellular structurecomprises cells distributed throughout the material at a lower densitythan a conventional polymeric foam. In one aspect of the material, theproportion of the cross-sectional area of the sheet that is solid andunfoamed is greater than the proportion of the cross-sectional area ofthe sheet that includes expanded cells. In contrast to a conventionalfoam material in which expanded cells extend one after anotherthroughout a given foamed section of the sheet, the materials and lidsaccording to one aspect of the present disclosure include expanded cellsthat are randomly distributed within the sheet and do not extendconsistently throughout a given section of the sheet. According to oneaspect of the present disclosure, treatment of the polyolefincomposition to decrease the density of the extruded sheet includesadding a blowing agent to the extrusion blend. According to anotheraspect, treatment to decrease the density includes a method of extrudingthe polyolefin composition to induce the formation of a plurality ofexpanded cells within the extruded sheet.

In accordance with one aspect, a blowing agent is added to thepolyolefin blend prior to extrusion to induce the formation of aplurality of expanded cells within the extruded sheet. The amount andtype of blowing agent is selected to provide a predetermined decrease inthe density of the extruded sheet. In one example, the amount and typeof blowing agent is selected to provide a decrease in density of about 5to 10% compared to a similar polyolefin blend, processed in a similarmanner, which does not include a blowing agent.

In another example, the amount and type of blowing agent is selected todecrease the density of the extruded sheet such that a lid formed fromthe sheet has a density less than 1 g/cm³ at 23° C. Unless otherwisestated, densities are given at 23° C. and atmospheric pressure. Having adensity less than 1 g/cm³ allows the lid to float on water, thusfacilitating recycling of the lid material using processes that rely onthe material to be recycled floating at or near the surface of therecycling stream. Optionally, the material can also be defined in termsof its specific gravity relative to water. The lid can be formed to havea specific gravity less than 1, relative to water at 23° C. andatmospheric pressure, such that the lid floats in water.

The blowing agent can be selected from any suitable chemical or physicalblowing agent compatible with the polyolefin(s) present in thepolyolefin composition. The blowing agent introduces gas (e.g., carbondioxide, nitrogen, steam) into the resin mixture to form an expandedcellular structure within the resin and reduce the density of theextrudate. According to one aspect of the present disclosure, theblowing agent can be a chemical blowing agent in the form of organic orinorganic materials that release gas upon thermal decomposition.Expansion of the cells in the resin mixture can occur during and/orafter extrusion. Non-limiting examples of suitable chemical blowingagents include sodium bicarbonate, sodium carbonate, ammoniumbicarbonate, ammonium carbonate, and ammonium nitrite. According to oneaspect, the blowing agent can be present in an amount of about 0.2 to 3wt. %, about 0.5-3 wt. %, optionally about 0.5-2 wt. %, furtheroptionally about 1-3 wt. %.

The amount and type of filler and the amount and type of blowing agentcan be selected in combination to provide an extruded sheet that can beformed into a lid having the desired physical properties suitable foruse as a hot food service lid and having a density less than 1 g/cm³,optionally less than 0.999 g/cm³, further optionally in the range ofabout 0.900 to 0.999 g/cm³ at 23° C. and atmospheric pressure.Optionally, the hot food service lid can be defined as having a specificgravity less than 1, relative to water at 23° C. and atmosphericpressure.

As the amount of filler added to the polyolefin blend increases, thereis an increase in the stiffness of the extruded polyolefin-based sheetand a concomitant increase in the density of the sheet and thus the lidformed using the polyolefin blend. If the density of the lid increasesto such an extent that the lid no longer floats in a recycling stream(i.e. the specific gravity of the lid relative to the water in therecycling stream is greater than 1), then the lid cannot be recycledusing this conventional recycling method. The addition of a blowingagent can offset this increase in density, allowing the filler to beselected from a broader range of amounts and types to provide thedesired stiffness for a hot food service lid while maintaining a densitysuitable for recycling the lid in a recycling stream.

For example, a polyolefin blend used to make the hot cup lid of FIG. 1that is based on polypropylene is generally limited to a mineral fillerloading of less than about 10-12 percent by weight (wt. %) in order tomaintain the ability of the lid to float in the recycling stream.However, this loading amount of mineral filler is not sufficient toincrease the stiffness of a polypropylene-based lid to an amountcomparable with a HIPS lid under hot food service conditions.

According to an aspect of the present disclosure, a polyolefin blendincluding polypropylene and a mineral filler in the range of about 12wt. % or greater, optionally about 15 wt. % or greater, optionally about18 wt. % or greater, further optionally about 20 wt. % or greater, stillfurther optionally about 25 wt. % or greater, and optionally in a rangeof about 20 wt. % to 25 wt. %, in combination with a blowing agentprovides a lid having a stiffness comparable to a HIPS lid incombination with a density less than 1 g/cm³. The blowing agent can bepresent in an amount of about 0.2-3 wt. %, optionally about 0.5-3 wt. %,optionally about 0.5-2 wt. %, further optionally about 1-3 wt. %, toprovide a decrease in lid density of about 5-10% compared to a similarlid formed in the absence of a blowing agent. The stiffness and densitycharacteristics can be maintained even in the presence of additives,such as colorants.

The extruded polyolefin-based sheet can be formed into a lid having thedesired shape and dimensions by thermoforming. Non-limiting examples ofthermoforming can include vacuum molding, pressure molding, plug-assistmolding, and vacuum snapback molding. The thermoforming process caninclude heating the polyolefin-based sheet (also referred to as a web)to a melting or softening temperature and then stretching or drawing thesheet over a mold. The web can be stretched or drawn over the mold whilethe web is still in a soft or molten state from the extrusion processwithout the application of heat from a heating unit. Optionally, thethermoforming process includes a heating unit, such as an oven, toreheat the web to a molten or soft state suitable for thermoforming. Thematerial can be maintained over the mold as the material cools andsolidifies to form the article. The formed article can then be trimmedfrom the thermoformed sheet and removed from the mold to form the lid.Optionally, the trimmed material is reground and processed for furtheruse as regrind, alone or in combination with virgin polyolefin.

The extruded sheet can be fed from the extruder to a molding stationwhere the thermoforming takes place or stored for further processing. Inone example, the sheet is fed from the extruder to the molding stationprior to the sheet cooling to room temperature and additional heat isoptionally supplied to the sheet prior to forming the sheet around themold. When the extruded sheet is stored prior to molding, heat issupplied to the sheet prior to forming the sheet around the mold. Heatfor facilitating molding of the sheet during thermoforming can besupplied in any suitable manner, examples of which include radiant heatand heated air. Optionally, the thermoforming process includes blowingair onto the sheet to facilitating pressing the sheet about the mold. Inanother example, the thermoforming process can include vacuum molding inwhich the sheet is forced against the mold by a vacuum. Thermoformingcan include a solid-phase forming process (e.g. using a reciprocatingformer) or a melt-phase forming process.

According to another aspect, the extrusion process of the polyolefinblend can be controlled to induce the formation of a plurality ofexpanded cells within the extruded sheet in the absence of a blowingagent. The polyolefin-blend can be extruded without venting or degassingto induce the formation of cells within the material. Without beinglimited to a particular theory, it is theorized that the absence ofventing or degassing during extrusion results in moisture present in theblend being converted to steam which can create cells in the extrudateas the steam travels through the material, thus forming the plurality ofexpanded cells. Mineral fillers present in the blend, such as talc, canact as nucleating agents to facilitate the formation of cells within theextrudate.

In an exemplary embodiment, the polyolefin blend can be extruded througha rotary extruder having a single stage screw with no venting ordegassing. The polyolefin blend can optionally include about 30-50% of apolyolefin regrind that includes a polyolefin and a mineral filler, suchas talc. It is theorized that the regrind may have a higher moisturecontent than virgin polypropylene and thus may facilitate formation ofthe cells during extrusion without venting/degassing. The polyolefinregrind can be recycled trimmed material and/or recycled waste lids thatis ground for inclusion in the polyolefin extrusion blend.

The extruded sheet formed without venting/degassing can be formed into alid by thermoforming in the same manner as described above.

EXAMPLES Example 1

FIGS. 2-3 are cross-sectional views of exemplary lids 100 and 120,respectively, according to an aspect of the present disclosure in whichthe polypropylene composition is treated to form a plurality of expandedcells formed therein to decrease the density of the polypropylene-basedlids 100 and 120 compared to a similar polypropylene-based lid 140 thathas not been treated to form an expanded cellular structure. Lids 100and 120 of FIGS. 2 and 3 , respectively, are made using a polyolefincomposition in accordance with an aspect of the present disclosureincluding polypropylene and about 18-19 wt. % of talc masterbatch (talccombined with a polypropylene carrier) as a mineral filler. The measuredtalc content in lid 100 and 120 was 13.1% and 11.8%, respectively, asdetermined using Thermal Gravimetric Analysis (TGA) according to ASTME1131 at 10° C./min.

Lid 100 was made using about 1.5 to 2.5 wt. % Hydrocerol 1499 fromClariant™ U.S.A. as a chemical blowing agent to form cells 102 in thelid body. The polypropylene blend for the lid 100 was extruded through arotary extruder having a single stage screw, with venting, andthermoformed as described above to shape the extruded sheet into theform of the lid 100. The lid 120 of FIG. 3 was made in a similar manner,except that the blend for lid 120 did not include a chemical blowingagent, and instead was extruded through a rotary extruder having asingle stage screw with no venting or degassing to form cells 122 in thelid body. The cells generally have an average diameter in the range ofabout 0.1 to 0.15 mm.

In contrast, the lid 140 of FIG. 4 was made using a polypropylene blendsimilar to that used to form the lid 120 and was extruded through arotary extruder having a single stage screw with venting. The lid 140was not formed from a blend that included a chemical blowing agent andwas not formed using an extrusion process that was unvented and thus thelid 140 does not include an expanded cellular structure. Polypropylenelids made without treatment to induce cell formation, such as the lid140, may include voids due to normal variations in processes andmaterials, e.g. such as induced by the filler particles. However, asillustrated by FIGS. 2-4 , the untreated polypropylene lid of FIG. 4does not exhibit the plurality of expanded cells demonstrated by thelids 100 and 120 of FIGS. 2 and 3 .

Example 2

An exemplary polyolefin composition in accordance with an aspect of thepresent disclosure includes polypropylene, about 18-19 wt. % of talc asa mineral filler, and about 1.5-2.5 wt. % Hydrocerol 1499 masterbatchfrom Clariant™, U.S.A. as a chemical blowing agent. Hydrocerol 1499 isdescribed by Clariant™, U.S.A. as a chemical foaming and nucleatingagent masterbatch. The polyolefin composition was extruded into a sheetusing conventional extrusion processes and thermoformed into a cup lidaccording to conventional thermoforming processes. The resultant cup lidhad a stiffness comparable to a similarly formed HIPS cup lid (similardimensions and part weight) and a density of about 0.95-0.96 g/cm³. Thepolypropylene-based lid floated on water. As used herein, density isdetermined at 23° C. and atmospheric pressure according to ASTM D-792.

Comparative Example 1

The polyolefin composition and cup lid of Example 1 except that thepolyolefin composition did not include a chemical blowing agent. Thecomparative cup lid had stiffness comparable to a similarly formed HIPScup lid (similar dimensions and part weight), but did not float onwater.

Example 3

Table 1 below illustrates the characteristics of three exemplarypolyolefin compositions for forming a cup lid according to an aspect ofthe present disclosure. In each of the Compositions 1-3, the polyolefinis a polypropylene homopolymer commercially available as Inspire® 6025Nfrom Braskem, U.S.A. The talc filler is commercially available as HT6HPfrom Heritage Plastics, which is described as 60% talc concentrated in apolypropylene homopolymer (masterbatch).

Each Composition 1-3 was extruded through a single stage screw rotaryextruder with no venting or degassing to form a sheet having pluralityof expanded cells. The sheet was used to form a cup lid having the shapeof the lid of FIG. 1 in a thermoforming process, as described above. Thetotal talc filler content in the lid was determined using both ThermalGravimetric Analysis (TGA) and Ash Content. The density of the lid wasdetermined using water displacement. TGA was conducted according to ASTME1131 at 10° C./min. Ash Content was conducted according to ASTM D3174.

TABLE 1 Characteristics of Lid with Expanded Cellular Structure WithoutChemical Blowing Agent Talc TGA Ash Masterbatch Residue Content DensityComposition (%) (%) (%) (g/cm³)* 1 17 8.9 9.5 0.933 2 30 13.0 19.4 0.9543 40 18.3 17.7 0.950 *The density for each Composition 1-3 is theaverage of two samples.

The data in Table 1 demonstrate that even as the talc filler contentincreases, the expanded cellular structure of the lid induced by notventing or degassing during extrusion facilitates maintaining thedensity of the cup lid at a value that is comparable to a much lowerfiller content. A similar lid formed using Compositions 2 and 3 in anextruder using a conventional process in which venting and degassing isperformed would be expected to have a density of at least about 1.02 to1.05 g/cm³.

FIG. 5 illustrates the ability of a lid according to the presentdisclosure to float in water. A lid made using Composition 2 of Table 1above was extruded through a single stage screw rotary extruder with noventing or degassing to form a sheet having plurality of expanded cells.The lid was formed from the sheet by thermoforming and then cut intopieces and placed in a bottle of water. The pieces of the lid were ableto float, indicative of the ability of the lid to be recycled from arecycling stream.

Example 4

Table 2 below illustrates the characteristics of four sample lids madeusing a polyolefin-based sheet according to an aspect of the presentdisclosure. Each of the PP Samples 1-4 were made using a polyolefinblend that includes a polypropylene homopolymer commercially availableas Inspire® 6025N from Braskem, U.S.A., 25 wt. % of HT6HP talcmasterbatch from Heritage Plastics, and about 1.5-2.5 wt. % Hydrocerol1499 masterbatch from Clariant™, U.S.A. as a chemical blowing agent. Thecomposition also includes 3 wt. % titanium dioxide as a colorant, anexample of which is commercially available as CH27043 2FA masterbatchfrom Ferro Corporation, U.S.A.

The polyolefin blend was extruded through a single stage screw rotaryextruder according to conventional extrusion processes to form a sheet.The sheet was used to form a cup lid having the shape of the lid of FIG.1 by thermoforming, as described above. The density of PP Samples 1-4was 0.932 g/cm³, as determined according to ASTM D-792.

HIPS Comparative Sample 1 is a conventional HIPS lid that was madeaccording to the same procedures as PP Samples 1-4, except the extrusionblend included HIPS instead of polypropylene and was free of a chemicalblowing agent.

The stiffness of the PP Sample and HIPS Comparative Sample lids wereanalyzed using a hot deflection test which measures the weight requiredto deflect the lid by 0.25 inches (6.4 mm) at two different points onthe lid. The hot deflection test was conducted on lids that were placedon a coffee cup holding coffee at 200° F. (93° C.). FIG. 6 illustratesthe locations, Point A and Point B, on the lid 10 at which thedeflection tests were conducted.

TABLE 2 PP Lid with Chemical Blowing Agent Compared to HIPS Lid 0.25″Hot Deflection (kg) Lid Weight Point A Point B PP Sample 1 4.34 2.6872.222 PP Sample 2 4.35 2.736 2.183 PP Sample 3 4.35 2.691 2.118 PPSample 4 4.35 2.821 2.000 HIPS Comparative 4.17 2.541 1.836 Sample 1

The hot deflection data in Table 2 demonstrates that the PP Samples 1-4made according to the present disclosure have at least comparablestiffness to a conventional HIPS lid, and even improved stiffness insome instances, in a hot beverage setting. The PP Samples also have acomparable part weight to that of the conventional HIPS lid. The PPsamples 1-4 also exhibit lid retention and leak resistancecharacteristics similar to the conventional HIPS lid. The data in Table2 demonstrates that the PP lids made according to the present disclosureare suitable for replacement of HIPS lids in a hot food service setting.

Similar PP lids without the talc filler of PP Samples 1-4 are softerthan the HIPS Comparative Sample and thus do not demonstrate thestiffness, lid retention, and leak resistance characteristics suitablefor a lid that can replace a conventional HIPS lid. The addition of thefiller to the polyolefin blend of the present disclosure provides a lidhaving the stiffness, lid retention, and leak resistance characteristicssuitable for replacement of a conventional HIPS lid.

The addition of the blowing agents to the polyolefin blend provides thePP Samples with a plurality of expanded cells and a density reductioncompared to a lid that does not have a plurality of expanded cells.Because the density of the PP samples is less than 1 g/cm³, the PPSample lids can float in a recycling stream, thus providing a polyolefinlid that has the stiffness, lid retention, and leak resistancecharacteristics suitable for replacement of a conventional HIPS lid andwhich is also recyclable.

In addition, the PP Sample lids according to the present disclosure havea matte finish that is aesthetically pleasing to consumers. The expandedcellular structure is generally not visible or minimally visible to thenaked eye. A low gloss level of about 15 gloss units or less generallycorrelates with a matte or paper-like finish aesthetic.

The following clauses define additional aspects of the presentdisclosure which are encompassed herein. These aspects can be combinedas desired to form combinations that are encompassed by the presentdisclosure.

A lid for a food or beverage container according to an aspect of thepresent disclosure is made from a sheet formed from an extrudedcomposition comprising at least one polyolefin, at least one filler, anda blowing agent, wherein the sheet has a thickness of 0.035 inches (0.9mm) or less and plurality of expanded cells formed within the sheet. Thelid can optionally include any one or any combination of the followingfeatures according to an aspect of the present disclosure: thepolyolefin can be selected from the group consisting of polypropylenehomopolymer, polypropylene impact copolymers, ethylene-propylenecopolymers, high density polyethylene, and combinations thereof; the atleast one filler can be selected from talc, calcium carbonate, mica,wollastonite, wood fiber, paper powder, cellulose fiber, andcombinations thereof; the sheet can have a thickness in the range ofabout 0.015 to 0.018 inches (0.4 to 0.46 mm); the filler can be presentin an amount of at least 12 wt. % or greater; the blowing agent can be achemical blowing agent selected from the group consisting of sodiumbicarbonate, sodium carbonate, ammonium bicarbonate, ammonium carbonate,and ammonium nitrite; the blowing agent can be present in an amount ofabout 0.2 to 3 wt. %; and/or a specific gravity of the lid can be lessthan 1 relative to water at 23° C.

A polyolefin-based extruded sheet according to an aspect of the presentdisclosure can include at least one polyolefin, at least one filler,wherein the at least one filler is present in an amount such that atotal amount of filler is 12 wt. % or greater, and a thickness of 0.035inches (0.9 mm) or less, wherein the extruded sheet has a plurality ofexpanded cells such that a density of the extruded sheet is less thanwater at 23° C. The polyolefin-based extruded sheet can optionallyinclude any one or any combination of the following features accordingto an aspect of the present disclosure: the polyolefin can be selectedfrom the group consisting of polypropylene homopolymer, polypropyleneimpact copolymers, ethylene-propylene copolymers, high densitypolyethylene, and combinations thereof; the polyolefin can include apolypropylene having a flexural modulus of at least about 290,000 psi;the polyolefin can include a polypropylene having a heat deflectiontemperature of at least 95° C.; the at least one filler can be selectedfrom talc, calcium carbonate, mica, wollastonite, wood fiber, paperpowder, cellulose fiber, and combinations thereof; the total amount ofthe at least one filler is 18 wt. % or greater; the plurality ofexpanded cells include cells having an average cell diameter in therange of about 0.01 to 0.15 mm; the at least one polyolefin can becombined with a blowing agent during extrusion to expand the polyolefin;the density can be in the range of about 0.900 to 0.999 g/cm³; and/orthe sheet can have a shrinkage rate of about 1.3 to 1.5% during storage.

A process for forming a lid for a food or beverage container accordingto an aspect of the present disclosure includes the following: providinga polyolefin blend including at least one polyolefin and at least onefiller to an extruder; extruding the polyolefin blend to form apolyolefin-based sheet, wherein the extruding takes place withoutventing or degassing; expanding the polyolefin-based sheet to form aplurality of expanded cells; and forming the expanded polyolefin-basedsheet into the shape of a lid, wherein the lid has a density less thanwater at 23° C. The process can optionally include any one or anycombination of the following features: the polyolefin can be selectedfrom the group consisting of polypropylene homopolymer, polypropyleneimpact copolymers, ethylene-propylene copolymers, high densitypolyethylene, and combinations thereof; the polyolefin can include apolypropylene having a flexural modulus of at least about 290,000 psi;the polyolefin can include a polypropylene having a heat deflectiontemperature of at least 95° C.; the at least one filler can be selectedfrom talc, calcium carbonate, mica, wollastonite, wood fiber, paperpowder, cellulose fiber, and combinations thereof; a total amount of theat least one filler can be about 12 wt. % or greater; thepolyolefin-based sheet can be expanded to decrease the density by about5 to 10%; the plurality of expanded cells can include cells having anaverage cell diameter in the range of about 0.01 to 0.15 mm; a stiffnessof the lid can be comparable to a similar lid made from unexpanded highimpact polystyrene, wherein stiffness is based on a weight required toinduce a 0.25 inch (6.4 mm) deflection of the lid when the lid is placedon a cup holding liquid at 200° F. (93° C.); the density can be in therange of about 0.900 to 0.999 g/cm³; the polyolefin-based sheet can havea shrinkage rate of about 1.3 to 1.5% during storage; the expandedpolyolefin-based sheet can have a thickness of 0.035 inches (0.9 mm) orless; and/or the polyolefin-blend can include about 30 to 50% regrindmaterial including a polyolefin and a filler.

A method of thermoforming a lid according to an aspect of the presentdisclosure includes heating a sheet including at least one polyolefinwith at least one filler, wherein the sheet has a plurality of expandedcells providing the sheet with a density of less than 1 g/cm³ at 23° C.,applying the heated sheet about a lid mold to form at least one lid inthe sheet, and removing the formed at least one lid from the sheet. Themethod can optionally include any one or any combination of thefollowing features: forming the sheet with an extruder; feeding thesheet from the extruder to the lid mold; forming the sheet with anextruder also effects the heating of the sheet; the extruder providesthe sheet as a molten sheet to a lid mold; forming the sheet with anextruder can include extruding a composition comprising the at least onepolyolefin, at least one filler, and a blowing agent; forming the sheetwith an extruder can include extruding the at least one polyolefin andat least one filler without venting or degassing during extrusion; theheating can include radiantly heating the sheet; applying the heatedsheet can include blowing air on the sheet to press the sheet about themold; the sheet can have a thickness of 0.035 inches (0.9 mm) or less;the lid can have a shrinkage rate of about 1.3 to 1.5% after the formedlid is removed from the sheet; the polyolefin can be selected from thegroup consisting of polypropylene homopolymer, polypropylene impactcopolymers, ethylene-propylene copolymers, high density polyethylene,and combinations thereof; the polyolefin can include a polypropylenehaving a flexural modulus of at least about 290,000 psi; the polyolefincan include a polypropylene having a heat deflection temperature of atleast 95° C.; the at least one filler can be selected from talc, calciumcarbonate, mica, wollastonite, wood fiber, paper powder, cellulosefiber, and combinations thereof; and/or a total amount of the at leastone filler can be 12 wt. % or greater.

To the extent not already described, the different features andstructures of the various aspects of the present disclosure may be usedin combination with each other as desired. For example, one or more ofthe features illustrated and/or described with respect to one of theaspects of the present disclosure can be used with or combined with oneor more features illustrated and/or described with respect to the otheraspects. That one feature may not be illustrated in all aspects of thepresent disclosure is not meant to be construed that it cannot be, butis done for brevity of description. Thus, the various features of thedifferent aspects may be mixed and matched as desired to form newaspects, whether or not the new aspects are expressly described.

While aspects of the present disclosure have been specifically describedin connection with certain specific aspects thereof, it is to beunderstood that this is by way of illustration and not of limitation.Reasonable variation and modification are possible within the scope ofthe forgoing disclosure and drawings without departing from the spiritof the present disclosure which is defined in the appended claims.

What is claimed is:
 1. A thermoformed lid for a food or beveragecontainer made from a non-vented, extruded sheet comprising at least onepolyolefin with at least one filler, and having a plurality of expandedcells providing the thermoformed lid with a density greater than 0 g/cm³at 23° C. and less than 1 g/cm³ at 23° C.
 2. The thermoformed lid ofclaim 1 wherein the at least one polyolefin is selected from the groupconsisting of polypropylene homopolymers, polypropylene impactcopolymers, ethylene-propylene copolymers, high density polyethylene,and combinations thereof.
 3. The thermoformed lid of claim 2 wherein thepolyolefin comprises a polypropylene having one of: a flexural modulusof greater than or equal to 290,000 psi; a heat deflection temperatureof at least 95° C.; or a combination of a flexural modulus of greaterthan or equal to 290,000 psi and a heat deflection temperature of atleast 95° C.
 4. The thermoformed lid of claim 1 wherein the at least onefiller is selected from talc, calcium carbonate, mica, wollastonite,wood fiber, paper powder, cellulose fiber, or combinations thereof. 5.The thermoformed lid of claim 1 wherein a total amount of the at leastone filler is greater than 12 wt. % of the sheet and less than or equalto 40 wt. % of the sheet.
 6. The thermoformed lid of claim 1 wherein astiffness of the thermoformed lid is comparable to a similarthermoformed lid made from unexpanded high impact polystyrene, andwherein stiffness is based on a weight required to induce a 0.25 inchdeflection of the thermoformed lid when the thermoformed lid is placedon a cup holding liquid at 200° F.
 7. The thermoformed lid of claim 1wherein the plurality of expanded cells have an average cell diameter inthe range of 0.01 to 0.15 mm.
 8. The thermoformed lid of claim 1comprising: a flexural modulus of greater than or equal to 290,000 psi,a heat deflection temperature of at least 95° C., a density in the rangeof 0.900 to 0.999 g/cm³, and a shrinkage rate of 1.3 to 1.5% duringstorage.
 9. The thermoformed lid of claim 1 wherein the expanded cellsare randomly distributed.
 10. A process for forming a lid for a food orbeverage container from a polyolefin-based sheet, the processcomprising: providing a polyolefin blend comprising at least onepolyolefin and at least one filler to an extruder; providing a blowingagent to the polyolefin blend; extruding, without venting, thepolyolefin blend to form a polyolefin-based sheet; and at leastpartially expanding the polyolefin-based sheet to form an expandedpolyolefin-based sheet having a plurality of expanded cells; and formingthe expanded polyolefin-based sheet into the shape of a lid; wherein thelid has a density less than water at 23° C.
 11. The process of claim 10wherein the polyolefin is selected from the group consisting ofpolypropylene homopolymers, polypropylene impact copolymers,ethylene-propylene copolymers, high density polyethylene, andcombinations thereof.
 12. The process of claim 10 wherein the polyolefincomprises a polypropylene having one of: a flexural modulus of at leastgreater than or equal to 290,000 psi; a heat deflection temperature ofat least 95° C.; or a combination of a flexural modulus of at leastgreater than or equal to 290,000 psi and a heat deflection temperatureof at least 95° C.
 13. The process of claim 10 wherein the at least onefiller is selected from talc, calcium carbonate, mica, wollastonite,wood fiber, paper powder, cellulose fiber, or combinations thereof. 14.The process of claim 10 wherein a total amount of the at least onefiller is greater than 12 wt. %.
 15. The process of claim 10 wherein thepolyolefin-based sheet is expanded to decrease the density by 5 to 10%.16. The process of claim 10 wherein the plurality of expanded cells hasan average cell diameter in the range of 0.01 to 0.15 mm.
 17. Theprocess of claim 10 wherein the lid comprises at least one of: astiffness of the lid is comparable to a similar lid made from unexpandedhigh impact polystyrene, and wherein stiffness is based on a weightrequired to induce a 0.25 inch deflection of the lid when the lid isplaced on a cup holding liquid at 200° F.; a shrinkage rate of 1.3 to1.5% during storage; or combinations thereof.
 18. The process of claim10 wherein the lid has a density in the range of 0.900 to 0.999 g/cm³.19. The process of claim 10 wherein the blowing agent is at least oneof: selected from the group consisting of sodium bicarbonate, sodiumcarbonate, ammonium bicarbonate, ammonium carbonate, and ammoniumnitrite; present in an amount of 0.2 to 3 wt. %; or combinationsthereof.
 20. The process of claim 10 wherein forming the expandedpolyolefin-based sheet into the shape of a lid comprises heating thesheet, applying the heated sheet a lid mold to form at least one lid inthe sheet, and removing the formed at least one lid from the sheet.